POS1325 CHRONIC RECURRENT MULTIFOCAL OSTEOMYELITIS (CRMO): NEW INSIGHTS INTO EXTRA-OSSEOUS MANIFESTATIONS.
Authors: M. Robert, C. Guillemin, L. Rossi-Semerano, C. Galeotti, I. Koné-Paut, P. Dusser
Journal: Annals of the Rheumatic Diseases (2022)

Background Chronic recurrent multifocal osteomyelitis (CRMO) is a rare inflammatory disease of the skeleton characterized by chronic and recurrent episodes of osteo-articular inflammation. The median age of onset is 10 years old. Clinical manifestations include musculoskeletal symptoms that are well described (pain, tenderness, swelling). Sometimes, skin lesions or digestive manifestations occur. Whole body magnetic resonance imaging (MRI) is the gold standard for assessing the multifocal pattern of the CRMO. Treatment is still empirical and mainly relies on non-steroidal anti-inflammatory drugs (NSAIDs). Bisphosphonates and biologics are used as second-line treatments. To date, the focus has been set on bone involvement and very few data are available on extra-osseous manifestations in CRMO. Objectives This study aims to further describe these extra-osseous clinical manifestations in CRMO. Methods A historical cohort was designed using 61 CRMO patients at the Pediatric Rheumatology Department in a tertiary university hospital in Paris (Hôpital Bicêtre, France). All patients underwent a MRI that confirmed the diagnosis according to the criteria of Jansson. Skeletal involvement was characterized with 1/axial, 2/ peripheral, 3/ axial and peripheral lesions. Extra-osseous manifestations were divided into 1/ skin lesions, 2/ gastro-intestinal manifestations, 3/ enthesitis and 4/ others. Pain was evaluated thanks to the Visual Analog Scale (VAS, from 0 to 10). Treatments used were recorded. The study complied with ethical requirements. Results Forty one patients were included in the study, with 31 females (75.6%). The mean ± SD age at onset was 79.1 ± 59.8 months, with a delay at diagnosis beyond six months (6.71 ± 6.96). Twenty-one patients had a familial history of inflammatory diseases (51.2%), with a majority of psoriasis or ankylosing spondylitis (n=13/21, 61.9%). At diagnosis, the level of pain was 5.71 ± 3.24. Eleven patients (42.3%) had blood inflammation. Bone lesions were reviewed thanks to whole body MRI: four patients had isolated axial involvement (10.0%), nine had peripheral involvement (22.5%) and 27 patients harbored both types of lesions (67.5%). The mean number of lesions was 6.65 ± 4.23. After 12 months of follow-up, all parameters regarding disease’s activity decreased (pain, blood inflammation, number of lesions). Regarding extra-osseous symptoms, fever occurred in seven patients (17.1%). Twenty-four patients had skin manifestations (58.5%) with palmoplantar lesions (n=3, 12.5%), acne (n=6, 25.0%), psoriasis (n=5, 20.8%) and aphthous (n=10, 41.7%). Four patients (9.76%) had gastro-intestinal symptoms and seven (17.1%) had enthesitis. One patient had uveitis. Almost all patients received NSAIDs (n=39/41, 95.1%) and half of the cohort were treated with bisphosphonates (n=21/41, 51.2%). Nine patients (22.0%) received biologics with a majority of TNF inhibitors. All patients that received TNF inhibitors had either a cutaneous involvement or digestive symptoms or enthesitis (Figure 1). Conclusion Extra-osseous manifestations have to be carefully searched in CRMO, especially in the presence of familial history of inflammatory diseases. While the severity of bone involvement can lead to use bisphosphonates, the introduction of biologics seems to rely on extra-osseous symptoms. These conclusions are drawn on a retrospective study and need to be confirmed in larger cohort. References [1]Wipff J, et al. A large national cohort of French patients with chronic recurrent multifocal osteitis. Arthritis Rheumatol 67, 1128-1137 (2015). [2]Jansson A, et al. Classification of Non-Bacterial Osteitis: Retrospective study of clinical, immunological and genetic aspects in 89 patients. Rheumatology 46, 154-160 (2006). Disclosure of Interests None declared